Although it is possible that the 215 cases with a diagnosis of neurofibromatosis without either specification or specific complications/symptoms included some cases of NF2, the mean age at death of these cases did not significantly differ from that of the other 418 cases with NF1, whereas the 23 cases excluded because of an evident or probable diagnosis of NF2 were significantly younger than the selected cases, which is consistent with the greater severity for NF2. This evidence concerns the gene NF1 and neurofibromatosis.